LR4-190F Polymeric PTC Resettable Fuse Equivalent & Substitute Parts

Part Overview

The LR4-190F is a polymeric PTC resettable fuse manufactured by Littelfuse Inc. in the PolySwitch® LR4 series. This component is rated for 15V maximum voltage with a 1.9A hold current and is packaged as a user-defined strap configuration. The part is active in production status and ROHS3 compliant. Equivalent and substitute parts are identified based on matching electrical characteristics, mechanical compatibility, and regulatory approvals to support design flexibility and supply chain continuity.

Key Parameters

Parameter	LR4-190F Value
Voltage - Max	15V
Current - Hold (Ih) (Max)	1.9 A
Current - Trip (It)	3.9 A
Current - Max	100 A
Time to Trip	5 s
Resistance - Initial (Ri) (Min)	39 mOhms
Resistance - Post Trip (R1) (Max)	102 mOhms
Operating Temperature	-40°C ~ 85°C
Type	Polymeric
Package / Case	Strap
RoHS Status	ROHS3 Compliant
Approval Agency	CSA, TUV, UL

Substitute Part Grouping Explanation

Substitute parts for the LR4-190F are classified into two functional categories based on electrical parameter compatibility:

Direct Electrical Equivalents maintain identical or near-identical hold current (Ih), trip current (It), voltage rating, and thermal response characteristics. These parts are interchangeable in applications where the original electrical performance envelope must be preserved.

Current-Rated Variants provide alternative hold current ratings within the same voltage class (15V) and package family. These parts are suitable for applications requiring different current protection thresholds while maintaining the same voltage protection level and operating temperature range.

Key Parameters Determining Substitution:

Voltage - Max: Must equal or exceed circuit voltage requirement
Current - Hold (Ih): Primary selection criterion for circuit protection level
Current - Trip (It): Determines fault response threshold
Resistance - Initial (Ri): Affects circuit performance during normal operation
Package / Case: Physical form factor compatibility
Operating Temperature: Environmental suitability
Approval Agency: Regulatory compliance requirements

Parameter Comparison

Part Number	Manufacturer	Voltage - Max	Current - Hold (Ih) (Max)	Current - Trip (It)	Resistance - Initial (Ri) (Min)	Resistance - Post Trip (R1) (Max)	Operating Temperature	Package / Case	Approval Agency
LR4-190F	Littelfuse Inc.	15V	1.9 A	3.9 A	39 mOhms	102 mOhms	-40°C ~ 85°C	Strap	CSA, TUV, UL
0ZSC0190FF1E	Bel Fuse Inc.	20V	1.9 A	3.9 A	39 mOhms	102 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-LR190	Bourns Inc.	15V	1.9 A	3.9 A	39 mOhms	102 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-LR260	Bourns Inc.	15V	2.6 A	5.8 A	20 mOhms	83 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-LR380	Bourns Inc.	15V	3.8 A	8.3 A	13 mOhms	37 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-S120	Bourns Inc.	15V	1.2 A	2.7 A	85 mOhms	220 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-S150	Bourns Inc.	15V	1.5 A	3 A	50 mOhms	113 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-S175	Bourns Inc.	15V	1.75 A	3.8 A	50 mOhms	120 mOhms	-40°C ~ 85°C	Strap	cURus, TUV
MF-MSMF050-2	Bourns Inc.	15V	500 mA	1 A	150 mOhms	1 Ohms	-40°C ~ 85°C	1812 (4532 Metric), Concave	cURus, TUV
MF-SM125-2	Bourns Inc.	15V	1.25 A	2.5 A	70 mOhms	250 mOhms	-40°C ~ 85°C	2-SMD	cURus, TUV
MF-SM150-2	Bourns Inc.	15V	1.5 A	3 A	60 mOhms	250 mOhms	-40°C ~ 85°C	2-SMD	cURus, TUV

Engineering Selection Recommendations

Direct Replacement (Strap Package, 1.9A Hold Current):

MF-LR190 (Bourns Inc., Multifuse® MF-LR series) is the primary direct electrical equivalent. It matches all critical electrical parameters: 15V voltage rating, 1.9A hold current, 3.9A trip current, and identical resistance characteristics. Both parts are ROHS3 compliant and hold TUV approval. This part is suitable for direct substitution in existing designs.

0ZSC0190FF1E (Bel Fuse Inc., 0ZSC series) provides electrical equivalence with a higher voltage rating (20V). The 1.9A hold current and 3.9A trip current match the LR4-190F. This part is suitable for applications where higher voltage margin is acceptable. Approval agencies differ (cURus, TUV vs. CSA, TUV, UL); verify compliance requirements for your application.

Current-Rated Variants (Strap Package, 15V):

MF-S175 (1.75A hold current) and MF-S150 (1.5A hold current) provide lower protection thresholds within the same voltage class and strap package. These are suitable for circuits requiring reduced current protection levels.

MF-LR260 (2.6A hold current) and MF-LR380 (3.8A hold current) provide higher protection thresholds. These are suitable for circuits requiring increased current capacity before protection activation.

MF-S120 (1.2A hold current) provides the lowest current protection option in the strap package family.

Surface Mount Alternatives (15V):

MF-MSMF050-2 (500mA, 1812 package) and MF-SM125-2 (1.25A, 2-SMD package) and MF-SM150-2 (1.5A, 2-SMD package) are surface mount configurations. These are suitable only if your design accommodates surface mount assembly and the specified package geometries. These parts are not mechanically compatible with strap-based through-hole designs.

All recommended substitutes are ROHS3 compliant and hold active product status.

Frequently Asked Questions (FAQ)

Q: Can I use 0ZSC0190FF1E as a direct replacement for LR4-190F?

A: Electrically, yes. The 0ZSC0190FF1E maintains identical hold current (1.9A), trip current (3.9A), and resistance characteristics. The higher voltage rating (20V vs. 15V) is backward compatible with 15V circuits. However, verify that cURus and TUV approvals satisfy your regulatory requirements, as the LR4-190F carries CSA, TUV, and UL approvals.

Q: What is the difference between MF-LR190 and LR4-190F?

A: Both parts are electrically identical: 15V, 1.9A hold current, 3.9A trip current, and matching resistance values. The primary differences are manufacturer (Bourns vs. Littelfuse) and approval agency combinations (cURus, TUV vs. CSA, TUV, UL). Mechanical dimensions are nearly identical (21.00mm length, 5.05mm vs. 5.20mm width).

Q: Can I substitute a surface mount part like MF-SM150-2 for the strap package LR4-190F?

A: No. Surface mount parts (MF-MSMF050-2, MF-SM125-2, MF-SM150-2) require different PCB assembly processes and cannot be mechanically installed in designs specified for strap packages. These are suitable only for new designs with surface mount capability.

Q: What does "hold current" mean, and why is it important for substitution?

A: Hold current (Ih) is the maximum continuous current the fuse allows without tripping. It is the primary selection criterion for PTC resettable fuses. Substituting a part with lower hold current may cause nuisance trips; substituting with higher hold current reduces protection effectiveness. Match hold current to your circuit's normal operating current.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All parts listed in this reference are ROHS3 compliant and suitable for applications with ROHS compliance requirements.

Q: What is the difference between trip current (It) and hold current (Ih)?

A: Hold current (Ih) is the maximum continuous current without activation. Trip current (It) is the threshold at which the fuse activates protection. The ratio between these values determines the fuse's sensitivity to overcurrent conditions. Both parameters must be considered when selecting substitutes.

Q: Can I use MF-LR260 or MF-LR380 if my circuit normally draws 1.9A?

A: These higher-rated parts (2.6A and 3.8A hold currents respectively) will not provide protection at 1.9A continuous current. They are suitable only for circuits designed to operate at their respective hold current ratings. Use them only if your circuit's normal operating current matches or is lower than the part's hold current specification.

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